Automated configuration of RF WLANs via selected sensors

ABSTRACT

In a wireless LAN (WLAN), methods, apparatuses and systems directed to facilitating configuration of a wireless network is provided. According to one implementation of the present invention, sensors are used to collect data associated with locations and other properties of access points of the wireless network. The collected data can then be used to assist in automatically configuring one or more aspects of the wireless network. In some implementations, the collected data can be used to dynamically re-configure the wireless network in real time. According to another implementation of the present invention, location computation mechanisms are used to collect data associated with the location of one or more wireless clients, and the data is used to dynamically adjust one or more radio frequency (RF) coverage maps in real time. The revised RF coverage maps can then be used to re-configure one or more operational parameters of the wireless network. Implementations of the present invention provide many advantages, such as automating the configuration of the wireless network in real time and facilitating network management decisions.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PATENTS

This application makes reference to the following commonly owned U.S.patent applications and/or patents, which are incorporated herein byreference in their entirety for all purposes:

U.S. patent application Ser. No. 10/407,584 in the name of Patrice R.Calhoun, Robert B. O'Hara, Jr. and Robert J. Friday, entitled “Methodand System for Hierarchical Processing of Protocol Information in aWireless LAN;”

U.S. patent application Ser. No. 10/794,842 in the name of Gregg Davi,Paul Dietrich, and Alexander H. Hills, entitled “Wireless Node LocationMechanism Responsive to Observed Propagation Characteristics of WirelessNetwork Infrastructure Signals;”

U.S. patent application Ser. No. 11/195,536 in the name of Brian Cox,Bruce McMurdo and Anuradha Gade, entitled “Method and System for DynamicAssignment of Wireless LAN Access Point Identity;”

U.S. patent application Ser. No. 10/315,410 in the name of DavidTheobold, and entitled “Access Point with Orientation Sensor;”

U.S. patent application Ser. No. 10/982,360 in the name of BhautikDoshi, Paul F. Dietrich and Gregg Scott Davi, and entitled “WirelessNetwork Management System Including Integrated Location Information;”

U.S. patent application Ser. No. 10/802,366 in the name of Paul F.Dietrich, Gregg Scott Davi and Robert J. Friday, and entitled “WirelessNode Location Mechanism Featuring Definition of Search Region toOptimize Location Computation;”

U.S. patent application Ser. No. 10/894,245 in the name of James Amos,entitled “Wireless Network Management with Antenna Control;”

U.S. patent application Ser. No. 10/407,372 in the name of Alexander H.Hills, Paul F. Dietrich and Robert J. Friday, and entitled “DynamicTransmit Power Configuration System for Wireless Network Environments;”

U.S. patent application Ser. No. 10/981,997 in the name of Bhautik Doshiand Patrice R. Calhoun, and entitled “Methods, Apparatuses and SystemsFacilitating Testing of Links to Mobile Stations in Wireless Networks;”and

U.S. patent application Ser. No. 10/982,153 in the name of Robert J.Friday, Paul F. Dietrich and Gregg Scott Davi, and entitled“Raster-to-Vector Conversion Operations Adapted to Modeling of RFPropagation.”

FIELD OF THE INVENTION

The present invention relates to wireless networks and, moreparticularly, to methods, apparatuses and systems directed tofacilitating configuration of wireless networks.

BACKGROUND OF THE INVENTION

Market adoption of wireless LAN (WLAN) technology has exploded, as usersfrom a wide range of backgrounds and vertical industries have broughtthis technology into their homes, offices, and increasingly into thepublic air space. This inflection point has highlighted not only thelimitations of earlier-generation systems, but the changing role WLANtechnology now plays in people's work and lifestyles, across the globe.Indeed, WLANs are rapidly changing from convenience networks tobusiness-critical networks. Increasingly users are depending on WLANs toimprove the timeliness and productivity of their communications andapplications, and in doing so, require greater visibility, security,management, and performance from their network.

As enterprises and other entities increasingly rely on wirelessnetworks, the proper deployment and configuration of wireless accesspoints in a wireless network environment becomes critical to performanceand security. One problem with wireless networks is that they arecomplicated to configure effectively and have traditionally requiredwireless experts to appropriately deploy and manage. The installation ofa WLAN typically involves the physical deployment of access points inone or more physical locations throughout a desired service region, theuse of site surveys and/or other analysis tools to assess theradio-frequency (RF) coverage provided by the deployed access points,and the configuration of operational parameters for each access point tooptimize operation of the wireless network. Furthermore, efficientoperation of wireless networks usually requires regular monitoring andadministration due to the dynamic nature of the RF environment in whichthe wireless access points operate.

Configuration of a wireless network is complicated because of theinherent attributes of RF propagation (typically in indoorenvironments), including multipath, interference, and other phenomenathat affect signal propagation and, thus, WLAN performance. As discussedabove, configuration of a wireless network involves setting, andsubsequently adjusting, a variety of operational parameters. Theseparameters may include, for example, RF channels, frequency bands (e.g.,IEEE 802.11a/b/g modes), transmit power, and receiver sensitivity.

During deployment of a wireless network, access points (APs) arephysically installed in selected locations, depending on where users areexpected or predicted to use their wireless devices. WLAN deploymentsmay span hundreds to thousands of APs to provide wireless coverage andmobility services for a large user base associated with enterprises orwireless service providers offering wireless hotspots. After the APs arephysically placed in their selected locations, a network administratormay then construct a model of the RF environment, including the locationof walls and other obstructions, to assist in configuring one or moreoperational parameters for the APs. Site surveys and RF prediction canthen be used to assess the expected RF coverage provided by the deployedaccess points. For example, the network administrator may manuallyconduct a site survey to assess the radio coverage and other performanceattributes of the wireless infrastructure. During a site survey, thenetwork administrator physically walks around selected locations orwalk-about points with a site survey tool and determines the signalstrength corresponding to each AP within the coverage area.

As discussed above, to ascertain the coverage and other performanceattributes of a wireless network deployment, RF prediction can also beused to construct site-specific models of RF signal propagation in agiven wireless network environment. RF predication can be used incombination with, or in lieu of, site surveys. RF prediction usesmathematical techniques, such as ray tracing, to model the effects ofphysical obstructions, such as walls, doors, windows, and the like, onRF signal propagation in a given environment. For example, S. Fortune,“Algorithms for Prediction of Indoor Radio Propagation,” TechnicalMemorandum, Bell Laboratories (1998), disclose various algorithms thatcan be used to predict radio signal propagation. Valenzuela et al.,“Indoor Propagation Prediction Accuracy and Speed Versus Number ofReflections in Image-Based 3-D Ray-Tracing,” Technical Document, BellLaboratories (1998), describe algorithms for modeling RF signalpropagation in indoor environments. In addition, Rajkumar et al.,“Predicting RF Coverage in Large Environments using Ray-Beam Tracing andPartitioning Tree Represented Geometry,” Technical Document, AT&T BellLaboratories (1995), also disclose methods for predicting RF signalpropagation in site specific environments.

With an RF model of the environment in which a WLAN is deployed, knownprocesses and algorithms can be used to compute a suggested set ofoperational parameters for the access points of the WLAN, such aschannel and transmit power assignments designed to optimize coverage andreduce interference. However, in known prior art systems, theconstruction of an RF model of a WLAN (either by site survey or RFprediction) typically involves the manual entry of a variety of datapoints, such as the location of the APs within the physical environment,antenna types, antenna gain, and sometimes the orientation of theantennas corresponding to the APs. Unfortunately, manual entry of thisinformation is inconvenient, repetitive and error-prone, especiallywhere there are a large number of APs.

As discussed above, due to the changing nature of an RF environment(such as changing or new sources of RF interference), a WLAN typicallyrequires constant monitoring to ensure adequate performance. To monitorthe wireless network, the network administrator may perform additionalsite surveys to assess the performance of the WLAN and/or the accuracyof the RF model used to configure the WLAN. The administrator may thenuse the data collected during the site survey to fine tune orreconfigure the wireless network. The optimization of a wireless networkis difficult because of all of the considerations involved. Optimizationof a wireless network is time consuming not only because of the inherentattributes of RF propagation, as discussed above, but also because it isan iterative process, as the multitude of measurements may becomeoutdated as soon as the environment changes. For example, if equipmentor furniture (e.g., a file cabinet) in a building is moved, theperformance of the wireless network may change. Accordingly, whenconfiguration of the wireless network becomes outdated, a new RF model(potentially involving additional site surveys and analysis) may berequired.

In light of the foregoing, a need in the art exists for methods,apparatuses, and systems that facilitate automatic configuration ofwireless networks. Embodiments of the present invention substantiallyfulfill this need.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of the components in a wirelesslocal area network system according to one embodiment of the presentinvention.

FIG. 2 is a functional block diagram illustrating the components of awireless network management server in accordance with an embodiment ofthe present invention.

FIG. 3 is a functional block diagram illustrating the components of anaccess point in accordance with one embodiment of the invention.

FIG. 4 is a diagram illustrating an exemplary floor plan of a buildingin accordance with one implementation of the present invention.

FIG. 5 is a flow chart illustrating a method implemented at an accesspoint in accordance with one embodiment of the invention.

FIG. 6 is a flow chart illustrating a method for determining therelative location of one or more access points in accordance with oneembodiment of the invention.

FIG. 7 is a flow chart illustrating a method for determining therelative location of a wireless client in accordance with one embodimentof the invention.

FIG. 8 is a flow chart illustrating a method for updating an RF coveragemap in accordance with one embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT(S)

A. Overview

The present invention provides methods, apparatuses and systems directedto facilitating the configuration of a wireless network. According toone implementation of the present invention, sensors are used to collectdata associated with locations and other properties of access points ofthe wireless network. Some implementations reduce the need for manualentry of configuration information, such as access point location,antenna orientation and the like. The collected data can then be used toassist in automatically configuring one or more aspects of the wirelessnetwork. In some implementations, the collected data can be used todynamically re-configure the wireless network in real time. According toanother implementation of the present invention, location computationmechanisms are used to collect data associated with the location of oneor more wireless clients, and the data is used to dynamically adjust oneor more radio frequency (RF) coverage maps in real time. The revised RFcoverage maps can then be used to re-configure one or more operationalparameters of the wireless network. As discussed in more detail below,implementations of the present invention provide many advantages, suchas automating the configuration of the wireless network in real time andfacilitating network management decisions.

B. Exemplary Wireless Network System Architecture

B.1. Network Topology

A wireless local area network (WLAN) system according to principles ofthe present invention is shown in FIG. 1. In a specific embodiment ofthe present invention, the system 100 includes a WLAN management module10, running on a WLAN management server 20 (also referred to herein aswireless network management server 20), a local area network (LAN) 40, arouter 45, and access points (APs) 50 a, 50 b, 50 c, 50 d, 50 e(collectively referred to as APs 50). As FIG. 1 illustrates, thesenetwork elements are operably connected to a network 44 via router 45.FIG. 1 illustrates one possible network environment in which theinvention may operate. Network 44, in one implementation, generallyrefers to a computer network, such as a LAN, a WAN, etc., that includesone or more intermediate network devices (e.g., routers, switches,etc.), which allow for the transmission of messages between WLANmanagement server 20 and APs 50. Of course, network 44 can include avariety of network segments, transmission technologies and components,such as Ethernet links, terrestrial WAN links, satellite links, andcellular links. LAN 40 may be a LAN or LAN segment implemented by anEthernet switch (not shown) (or an array of switches) having multipleports to which APs 50 are connected. The APs 50 are typically connectedto the switch ports via Ethernet links; however, other link layerconnection protocols or communication means can be employed. Otherimplementations are possible. For example, although WLAN managementserver 10 is illustrated as being on a different LAN or LAN segment, itmay be co-located with APs 50.

The APs 50 are operative to wirelessly communicate with remote wirelessclient devices 60 a; 60 b (collectively referred to as “clients” 60). Inone implementation, the APs 50 implement the wireless network protocolspecified in the IEEE 802.11 WLAN standard, including all amendmentsthereto. The APs 50 may be autonomous or so-called “fat” APs, orlight-weight APs operating in connection with a wireless switch (notillustrated), as disclosed in U.S. patent application Ser. No.10/407,584, now U.S. Pat. No. 7,212,837.

B.2. Wireless Network Management Server

As FIG. 2 shows, in one implementation, WLAN management server 20comprises a processor 902, a system memory 914, a network interface 924,and one or more software applications (including the WLAN managementmodule 10 shown in FIG. 1) and drivers enabling the functions describedherein. Furthermore, the WLAN management module 10, in oneimplementation, may comprise a Wireless LAN Solution Engine (WLSE)offered by Cisco Systems, Inc. of San Jose, Calif. As discussed in moredetail below, WLAN management module 10, in one implementation, includesvarious software modules that collect sensor and other data from theaccess points and compute various WLAN configuration parameters. In someimplementations, WLAN management module 10 employs an RF model of theWLAN deployment environment to compute one or more operationalparameters for the APs 50. In some implementations, WLAN managementmodule 10 is also operative to coordinate various operations, performedby the access points 50, related to data gathering, such as switching toa common channel, and the transmission of packets between the accesspoints in order to perform various RF measurements. The software modulesmay also include HTTP or other server functionality allowing networkadministrators to access WLAN management module 10 from remote stations.

The present invention can be implemented on a wide variety of computersystem architectures. For example, FIG. 2 illustrates, for didacticpurposes, hardware system 900 having components suitable for wirelessnetwork management server 20 in accordance with an implementation of thepresent invention. In the illustrated embodiment, the hardware system900 includes processor 902 and a cache memory 904 coupled to each otheras shown. Additionally, the hardware system 900 includes a highperformance input/output (I/O) bus 906 and a standard I/O bus 908. Hostbridge 910 couples processor 902 to high performance I/O bus 906,whereas I/O bus bridge 912 couples the two buses 906 and 908 to eachother. Coupled to bus 906 are network/communication interface 924, andsystem memory 914. The hardware system may further include video memory(not shown) and a display device coupled to the video memory. Coupled tobus 908 are mass storage 920 and I/O ports 926. The hardware system mayoptionally include a keyboard and pointing device (not shown) coupled tobus 908. Collectively, these elements are intended to represent a broadcategory of computer hardware systems, including but not limited togeneral purpose computer systems based on the Pentium® processormanufactured by Intel Corporation of Santa Clara, Calif., as well as anyother suitable processor.

The elements of computer hardware system 900 perform their conventionalfunctions known in the art. In particular, network interface 924 is usedto provide communication between system 900 and any of a wide range ofnetworks, such as an Ethernet (e.g., IEEE 802.3) network, etc. Massstorage 920 is used to provide permanent storage for the data andprogramming instructions to perform the above described functionsimplemented in the system controller, whereas system memory 914 (e.g.,DRAM) is used to provide temporary storage for the data and programminginstructions when executed by processor 902. I/O ports 926 are one ormore serial and/or parallel communication ports used to providecommunication between additional peripheral devices, which may becoupled to hardware system 900.

Hardware system 900 may include a variety of system architectures, andvarious components of hardware system 900 may be rearranged. Forexample, cache 904 may be on-chip with processor 902. Alternatively,cache 904 and processor 902 may be packed together as a “processormodule,” with processor 902 being referred to as the “processor core.”Furthermore, certain implementations of the present invention may notrequire or include all of the above components. For example, theperipheral devices shown coupled to standard I/O bus 908 may be coupledto high performance I/O bus 906. In addition, in some implementationsonly a single bus may exist with the components of hardware system 900being coupled to the single bus. Furthermore, additional components maybe included in system 900, such as additional processors, storagedevices, or memories.

As discussed above, in one embodiment, the operations of the wirelessnetwork management server 20 described herein are implemented as aseries of software routines run by hardware system 900. These softwareroutines comprise a plurality or series of instructions to be executedby a processor in a hardware system, such as processor 902. Initially,the series of instructions are stored on a storage device, such as massstorage 920. However, the series of instructions can be stored on anyconventional storage medium, such as a diskette, CD-ROM, ROM, etc.Furthermore, the series of instructions need not be stored locally, andcould be received from a remote storage device, such as a server on anetwork, via network/communication interface 924. The instructions arecopied from the storage device, such as mass storage 920, into memory914 and then accessed and executed by processor 902.

An operating system manages and controls the operation of system 900,including the input and output of data to and from software applications(not shown). The operating system provides an interface between thesoftware applications being executed on the system and the hardwarecomponents of the system. According to one embodiment of the presentinvention, the operating system is the Windows® 95/98/NT/XP operatingsystem, available from Microsoft Corporation of Redmond, Wash. However,the present invention may be used with other operating systems, such asthe Apple Macintosh Operating System, available from Apple Computer Inc.of Cupertino, Calif., UNIX operating systems, LINUX operating systems,and the like.

B.3. Access Point

FIG. 3 is a functional block diagram illustrating the components of anAP 50 in accordance with one implementation of the present invention. AnAP 50 comprises a processor 310, a memory 312, a network interface 314(e.g., an 802.3 interface) for communication with a LAN, a wirelessnetwork interface 316 (e.g., an IEEE 802.11 WLAN interface) for wirelesscommunication with one or more wireless clients 60, a persistent memory318, an optional input/output (I/O) port 320 for communication with anoptional global positioning system (GPS) device or equivalent 322, andoptionally one or more orientation sensors 323 associated with one ormore antennas 324 (e.g., omni-directional or directional antennas)corresponding to the wireless network interface 316, antennainterrogator 325 associated with the one or more antennas 324, and asystem bus 308 interconnecting these components. The APs 50 also includesoftware modules (including DHCP clients, Cisco® Discovery Protocol(CDP) modules, AP modules, SNMP functionality, etc.) and device drivers(e.g., network and WLAN interface drivers) stored in the persistentmemory 318 (e.g., a hard disk drive, flash memory, etc.). At start up,these software components are loaded into memory 312 and then accessedand executed by processor 310.

In operation, the orientation sensors 323 detect the orientation of oneor more antennas 324 of the AP. More specifically, the orientationsensors, in one implementation, are mounted directly to correspondingantennae 324, and are operative to determine the orientation of theantennae 324 with respect to magnetic “compass points,” and optionallythe local measure of elevation angle relative to the horizon. In anotherimplementation, orientation sensors can be used within the AP housing toascertain the orientation/elevation of the AP housing, with relativeorientation sensors (e.g. potentiometers) indicating the orientation ofthe antennae 324 relative to the AP housing. Using this combination ofabsolute and relative sensors, the absolute orientation(s) of theantenna(s) 324 can be determined. In a third implementation, one set ofabsolute orientation sensors are mounted to one antenna 324, whilerelative orientation sensors are mounted to the AP housing and the otherantennae attached to the AP housing. The orientation sensors 323 canalso be used to reference the antenna 324 with respect to any localcoordinate system, e.g., the floor plan of a building or otherpredetermined bounded area. In one implementation, the orientationsensors 323 can initially determine the orientation of the antenna 324at the time of deployment and specifically the orientation of theantenna 324 relative to other antennas in the wireless network system.Where there are measures of relative angle between the AP housing andassociated antennae, a measure of elevation angle relative to thehorizon of the antenna 324 can optionally be used to ascertain thephysical orientation of the AP housing, which is useful in ascertainingthe orientation of the complement of antennas on the housing. Inaddition, the orientation sensors 323 can optionally be used toperiodically confirm the orientation of the antenna 324, in the eventthat the antenna 324 might be moved or disturbed in an enterpriserollout.

In one implementation, the orientation sensors 323 can be a magneticsensor located within the AP and, optionally, a one- or two-axiselevation sensor. Other antenna orientation sensors can also be usedthat do not derive the orientation of the antenna relative to the APhousing. A reference point is noted within the AP housing so that theradio/antenna pairs within the AP might be indexed. A two- or three-axismagnetic sensor is preferably incorporated to measure the magnetic fieldof the Earth relative to that reference point. In order to obtain a moreprecise directional resolution, the magnetic declination of thedeployment location may be calculated in order to calibrate the magneticsensor. In one implementation, this requires a (crude) absolutelocation, such as obtained by GPS or if coverage is unavailable, bymanual-entry of the deployment address. In this way, a very sensitiveand precise measurement of the directional orientation of the AP may beobtained. Optionally, one or two elevation angle (gravitational) sensorsmay be used to provide a local measure of elevation angle in one or twoaxes relative to the horizon.

A variety of implementations could be employed as orientation sensors323, and would provide a number of respective advantages and engineeringtradeoffs. Such implementations would include but not be limited toposition sensing magnetic floats, Hall-effect devices, fluxgatemagnetometers, dielectric fluid clinometers, and pendulum sensors. Anysuitable measurement circuitry, either digital or analog, could be usedto process the orientation information. For example, the sensormeasurement could be processed as a subroutine in the AP to be read asany other status command to provide the orientation information. Theorientation information may also be stored in a MIB for access via SNMPqueries. Alternatively, the sensor measurement could be forwarded to aremote server or other component on the wireless network. In eithercase, the orientation information could be maintained in a centraldatabase for maintaining the directional orientations of all the APsassociated with the wireless network. U.S. patent application Ser. No.10/315,410 entitled “Access Point with Orientation Sensor”, incorporatedby reference herein, discloses orientation sensors that detect theorientation of an AP.

The antenna control data sensors 325 detect other properties andparameters of the one or more antennas 324 of the AP. As described morefully below, the properties and parameters may include predeterminedantenna gain, antenna type (e.g., dipole, omnidirectional, patch), brandname, model number, part number, etc. U.S. patent application Ser. No.10/894,245 entitled “Wireless Network Management with Antenna Control,”incorporated by reference herein, discloses antennas that providecontrol data, and using antenna control data to facilitate management ofa wireless network.

C. Automatic Configuration of a Wireless Network

In one implementation of the present invention, sensors are used tocollect data associated with the absolute and relative locations, andother properties of APs deployed in the wireless network. Morespecifically, as described in further detail below, a two-phase locationprocess is used to automatically discover AP location. In a first phase,the APs, upon start up or other event, attempt to discover theirabsolute geographic locations using GPS sensors, when possible. Duringthis first phase, the APs may also poll antenna orientation and controldata sensors to gather antenna orientation and control data. In a secondphase, the locations of the APs relative to each other are determinedusing signal strength, Time of Arrival (TOA) and/or Time Difference ofArrival (TDOA) techniques, as described more fully below, or otherproprietary location technologies, such as infra-red, laser, theproperties of low-frequency near-field signals (Q-track),ultrasound-base location technologies, etc. In one implementation,signal strength data from the APs may be obtained using functionalityavailable on standard 802.11 chip sets that collect signal strength databy measuring the strength of signals during receipt of wireless framestransmitted between the APs. The collected signal strength and/orlocation data is used to compute the geographic locations of the APs.The location data and optionally the antenna orientation data collectedby the sensors may then be used to construct an RF model of the WLANdeployment environment. This RF model may be used to automaticallycompute RF operational parameters to dynamically configure the wirelessnetwork without requiring manual entry of various AP attributes, such asthe physical location of the access points, as well as the attributesand orientation of the antennas, etc.

FIG. 4 is a diagram illustrating an exemplary floor plan of a building400 in accordance with one implementation of the present invention. AsFIG. 4 shows, the building 400 includes windows 402 positioned aroundthe perimeter of building 400 and walls 404 positioned in variouslocations inside building 400. Also, APs 50 are positioned in variouslocations inside building 400. As described above, in oneimplementation, GPS devices connected to the APs 50 can be used todetermine the absolute locations of the APs. However, a problem with GPStechnology is that the strength of the GPS radio signals, propagatingthrough the walls of building 400 (and potentially other obstructions),may not be sufficient to allow the GPS devices attached to the APs toreliably determine an absolute geographic location. Accordingly, the APs(e.g., 50 a, 50 c) near the edge of building 400 and particularly nextto windows 402 will most likely be the APs where the received GPSsignals are sufficient to get an accurate absolute geographic location.As long as one absolute geographic location is determined, the knownabsolute location(s), or “anchor” location(s), can then be used tocompute the geographic (i.e., absolute) locations of the other APs(e.g., 50 b, 50 d, 50 e) located in the central regions of building 400away from the windows 202 by using the relative location technologiesdescribed below. In a preferred embodiment, for unambiguous location intwo dimensions, the GPS devices determine at least three non-colinearabsolute locations, and in three dimensions, the GPS devices determineat least four non-coplanar locations.

C.1. Absolute Locations of Access Points

Access points 50, in one implementation, can be configured to pollvarious sensors and store data collected from the sensors in a datastore, such as a Management Information Base (MIB), for subsequentaccess by WLAN management module 10 (e.g., via SNMP queries or traps).As discussed in more detail below, the sensor data may include GPSlocation data, antenna control data and antenna orientation data. Asdiscussed above, various sensors may be used to automatically collectdata used to facilitate computing the absolute physical location (e.g.,global coordinates) of APs. Such data may be derived from ground-basedradio signals or satellite radio signals. For example, known globalcoordinate system devices, such as global positioning system (GPS)devices or equivalents, may be utilized to facilitate computing absoluteglobal coordinates of APs within feet and inches. That is, each AP, asillustrated in FIG. 3, may include a GPS receiver 322 that detects GPSradio signals and determines an absolute geographic location.

The use of radio signals to estimate the location of a wireless deviceor node is known. For example, a GPS receiver obtains geographiclocation information by trilaterating its position relative tosatellites that transmit radio signals. The GPS receiver estimates thedistance between each satellite based on the time it takes for the radiosignals to travel from the satellite to the receiver (i.e., timedifference of arrival (TDOA) calculations). Signal propagation time isassessed by determining the time shift required to synchronize thepseudo-random signal transmitted by the satellite and the signalreceived at the GPS receiver.

FIG. 5 is a flowchart illustrating a method for determining the absolutelocation of an AP in accordance with one implementation of the presentinvention. An AP performs the following process at start up (optionally,on a periodic basis after startup) and/or when the WLAN managementmodule 10 transmits a command. Additionally, each AP may obtain adynamic IP address and discover the WLAN management module 10 inprocesses performed prior to, concurrently with, or during the sensordata collection processed described herein. U.S. application Ser. No.11/195,536 discloses one possible method that allows an AP to discoverthe WLAN management module 10. As FIG. 5 illustrates, the AP polls theantenna control data sensors and stores the antenna control data in theMIB (502). The AP then polls the antenna orientation sensors and storesthe antenna orientation data in the MIB (504). The AP then determines ifa GPS location is available by polling its associated GPS device to seeif it identifies a geographic location (506). If so, the AP stores thegeographic location in the MIB (508). The WLAN management module 10 maysubsequently gather the absolute location via an SNMP query. If the GPSdevice does not return a geographic location, the AP may store a “nolocation” or null value in the corresponding MIB entry.

As described in detail below, the WLAN management module 10 maysubsequently determine the location of at least one AP relative to otherAPs. For example, if the WLAN management module 10 is trying todetermine the geographic location of a single, newly-added AP, and ifthe WLAN management module 10 does not find a GPS location in the MIB ofthe newly-added AP, or cannot otherwise determine an absolute location(e.g., after a predetermined number of tries or after a predeterminedamount of time), the WLAN management module 10 may then determine thelocation of the AP relative to other APs for which absolute geographiclocations are known. In another implementation, the WLAN managementmodule 10, in a configuration mode, may direct all APs to attempt GPSlocation, wait a sufficient amount of time for the APs to store thelocations, if any, in their respective MIBs, and then retrieve all thelocations. After collecting the absolute location data, the WLANmanagement module 10 may then direct a desired set of APs to transmitwireless frames, and collect data relating to the signals of wirelessframes transmitted by other APs in order to determine the location ofthe APs relative to each other. In one implementation, where GPS is notavailable or able to provide desired data, known manual procedures, suchas manually identifying the absolute geographic location of a subset ofthe APs, may be implemented before the relative location processdescribed below is initiated. Also, in another embodiment, such manualentry may follow the relative location determination proceduresdescribed below. Given that relative locations are already available (asper below), the first few APs are manually entered, then quickly otherAPs automatically place themselves (perhaps allowing the user tofine-tune their estimated locations).

C.2. Relative Locations of Access Points

Various sensors and mechanisms may also be used to collect data thatallows for a determination of the relative location of APs (e.g.,relative to other APs). As described in more detail below, the WLANmanagement module 10 can be configured to control some or all of the APsin a desired set of APs, coordinating their operation such that the APstransmit and receive packets and collect signal strength and/or time ofarrival data associated with the data transmissions of other APs. Thecollected data, at each AP, may include signal strength datacorresponding to neighboring APs, the arrival time of packetstransmitted by neighboring APs, and the like. With this data, variousrelative location technologies (e.g., time difference of arrival (TDOA),time of arrival (TOA), receive signal strength indicator (RSSI), otherproprietary schemes such as Q-track, etc.) can be used to compute therelative locations of the AP. TDOA and TOA are known technologies forcomputing the location of wireless nodes. As described more fully below,in one implementation, an AP unicasts or broadcasts packets toneighboring APs, where the differences in the transmission and receipttimes (or the received signal strength) are used to determine thedistances and, by trilateration, the locations, of the APs relative toeach other. In one implementation, the APs 50 are configured to use acommon point or segment in the signal carrying the wireless frames towhich the time stamp measurements are referenced. For example, thesignal reference point can be the Start of Frame Delimiter for DSSS orCCK packets according to the 802.11b/g WLAN standard, or the start ofthe long symbol sequence in the signal waveform of OFDM packetsaccording to the 802.11a standard. One skilled in the art willrecognize, however, that suitable reference points will depend on thewireless standard and the corresponding physical layer attributes of thewireless frames.

The wireless frames transmitted by the APs can include time stamps andsequence numbers to facilitate correlation and time of arrivalmeasurements of the frames as received by the neighboring APs. Asdescribed more fully below, in one implementation, an AP transmitspackets to neighboring APs, where resulting signal strength informationassociated with receipt of a frame is used to determine the locations ofthe APs relative to each other. The collection of receive signalstrength (RSSI) data is a standard-part of 802.11 chip sets. U.S. patentapplication Ser. No. 10/794,842 incorporated by reference herein,discloses how RSSI data can be used to locate wireless nodes. As FIG. 6illustrates, WLAN management module 10 can cause the APs totransmit/broadcast wireless frames in a coordinated fashion to allowneighboring APs to collect data (e.g., TDOA, TOA, and/or signal strengthdata). As described in detail below, these location technologies,individually or in combination, are used to compute relative locationsof APs, by estimating relative distances and using trilateration. Therelative location data can be used in combination with availableabsolute location data to compute the absolute location of accesspoints, where the GPS or other location sensor was unable to provideabsolute location data. For example (and referring to FIG. 4), withknowledge of the absolute location of APs 50 a, 50 c, located proximallyto windows, the absolute location of AP 50 d, for example, may bedetermined based on its location relative to AP 50 a and/or 50 c.

FIG. 6 is a flowchart illustrating a method for determining the relativelocation of an AP, in accordance with one implementation of the presentinvention. As FIG. 6 illustrates, the WLAN management module 10 selectsAPs (e.g. 50 a, 50 b, 50 c) for determining relative locations (602) andthen instructs the APs to switch to a uniform channel (e.g., a“transmit” channel) (604) to conduct a predetermined series of wirelessframe transmissions. In one implementation, the selected APs canbroadcast a series of packets (each including a unique sequence numberand possibly a time stamp), where each non-transmitting AP can recordthe sequence number, the arrival time, the signal strength correspondingto the packet, and the MAC address of the transmitting AP. In oneembodiment, a coarse arrival time and a waveform is stored and madeavailable to the WLAN management module for TOA post-processing (e.g.,cross-correlation or de-correlation) in order to obtain a fine arrivaltime. In another embodiment, the TOA post-processing is performedlocally so that only a fine arrival time is made available to the WLANmanagement module. The collision avoidance mechanisms provided by theIEEE 802.11 protocol can be used by the APs to coordinate their packettransmissions. To support TOA location, the transmitting AP can recordthe sequence number and the time of packet transmission; alternatively,the transmitting AP can include the time of packet transmission in thetransmitted wireless frames. All the data can then be stored in adatabase and transmitted to (or later read by) the WLAN managementmodule 10. The WLAN management module 10, in one implementation, waitsfor a predetermined amount of time after issuing commands to theselected APs to allow time for the APs to complete the transmissions anddata collection (606) and then gathers the data from the APs (608). TheWLAN management module 10 then processes the results (610) to computerelative locations of the APs and stores the relative locations inassociation with corresponding APs (612). In another implementation, theAPs can be configured to transmit the collected data to the WLANmanagement module 10 a threshold period of time after initiating thepacket transmissions. In one implementation, the WLAN management module10 can be configured to execute the relative location technologies on arepeated basis, during off-peak hours, to obtain accurateautocorrelation matrices needed for super-resolution techniques.

C.3. Attributes and Orientation of Antennas of Access Points

As discussed above, in addition to gathering data associated with theabsolute and relative location of the APs, the WLAN management module10, in one embodiment, also collects data associated with the attributesand orientation of each of the antennas of the APs. For example,attribute data may include properties and parameters such as antennagain, antenna type (e.g., dipole, omnidirectional, patch), brand name,model number, part number, etc. Other data may include, for example,elevation patterns, azimuth patterns, magnetic declination, etc. In oneimplementation of the present invention, any combination of differentattribute and orientation data may be detected in real time by sensors.For example, in one implementation, an antenna 324 may have a smallmicrocontroller that reads back antenna attributes to that AP 50 whichstores the data in a MIB. The WLAN management module 10 may then gatherthis information upon request or automatically as data is updated.Antenna orientation data may be collected by any one or combination of atilt sensor, a gravity-based tilt sensor, an azimuth sensor, a digitalcompass, potentiometer (POT), or other orientation sensor. The collectedattribute and orientation data may be stored in a database such as aMIB, which the WLAN management module 10 can later retrieve. Since eachantenna or AP/antenna combination is provided with sensors to identifythe antenna and its attributes and orientation, manual entry of antennaproperties can be avoided. U.S. patent application Ser. No. 10/315,410,incorporated by reference herein, discloses a sensor that detects howthe antenna of an AP is oriented. Further, U.S. patent application Ser.No. 10/894,245, incorporated by reference herein, discloses managementof a wireless network using antennas.

C.4. Real-Time Configuration of the Wireless Network

As described above, the WLAN management module 10 uses automaticallycollected data (i.e., the absolute and/or relative locations of someAPs, and optionally, the antenna configuration and/or orientation data),to compute the absolute geographic locations of all of the APs. Inaddition, with knowledge of one or more geographic location coordinatesof the desired coverage area, the APs can be located relative to thephysical attributes of the coverage area, such as the walls andpartitions in the floor plan illustrated in FIG. 4. The WLAN managementmodule 10 may then use the physical deployment data (i.e., locationdata, and optionally the antenna orientation data), as well as thephysical properties of the antennas) to compute an RF model of thedeployment environment and configuration data in real. For example, thecollected data may be used to construct a physical model of the WLANdeployment environment. RF prediction techniques can be used inconnection with the physical model to model expected RF propagationcharacteristics, generating RF propagation or heat maps, and computeconfiguration parameters for one or more of the APs. Configurationparameters may include information for optimizing transmit power andchannel allocations for APs. Another benefit of the present invention isthat the use of conventional site surveys can be avoided or minimized,since the wireless network can be automatically reconfigured using thedata collection processes discussed above to reflect changes in the RFenvironment.

D. Automatic Adjustments of an RF Coverage Map

In another implementation of the present invention, location computationmechanisms are used to collect data associated with the location of oneor more clients. The detected signal strength values can, as discussedin more detail below, be used to dynamically adjust one or more RFcoverage maps. The revised RF coverage maps may then be used todynamically re-configure one or more operational parameters of thewireless network. As a result, the WLAN management module 10 effectivelyuses clients as site survey tools to dynamically optimize and maintainthe wireless network.

D.1. RF Coverage Map

RF coverage maps, also referred to as radio coverage maps or heat maps,are known. RF coverage maps are typically derived from a manual sitesurvey, by RF prediction algorithms, or a combination of the two. In oneimplementation, an RF coverage map is represented as a table, ortwo-dimensional data array, where each element of the array represents alocation bin or small region of the physical RF environment. The valueof each element can represent the expected receive signal strength(given an assumed transmit power) at the location corresponding to eachelement or the expected signal attenuation (in dBs) at that locationrelative to an AP location. RF coverage maps can be maintainedseparately for each AP and combined as needed; however, in otherimplementations, RF coverage maps can include RF propagation data forall APs within the modeled region.

To define a coverage map, a network administrator configures the x- andy-coordinates corresponding to the location of the AP (and, in someimplementations, the angular orientation of the AP antenna(s)) thephysical region in which the AP is deployed. In one implementation, thisinformation can be automatically configured based on the automatic datacollection and location technologies discussed above. With the locationof the AP within the model of the physical space, and in someimplementations, other AP properties, such as antenna type, antennaorientation, radio type (e.g., 802.11a, 802.11b/g, etc.), the WLANmanagement module 10 may then compute an RF coverage map for the AP.That is, using an RF prediction tool, the WLAN management module 10 mayprocess a vector model (for example) of the region to obtain a model ofRF signal propagation characteristics from the defined AP locationwithin the region corresponding to the RF coverage map. The RF coveragemaps may also be derived using data obtained from a site survey.

The RF coverage maps are stored in a database and can subsequently beused to graphically display RF coverage information, or to locatewireless nodes, such as mobile stations and rogue APs. In oneimplementation, an RF coverage map characterizes, for a given AP, theexpected signal strength, or signal attenuation, at a given location. Inone implementation, an RF coverage map, for each AP, includes the signalstrengths or attenuations in an N×M matrix, where N is the number ofx-coordinate locations in the RF coverage map, and M is the number ofy-coordinate locations in the RF coverage map. For example, in oneimplementation, a RF coverage map or matrix indicates the expectedsignal strength received by a wireless node at given locations definedin x-, and y-coordinates. In one implementation, the extent of thephysical space modeled by the RF coverage maps for each AP isco-extensive with the area map of the region in which the AP isdeployed. In other implementations, the RF coverage maps for the APs canextend to a boundary configured by a network administrator or determinedby a signal strength threshold.

As discussed above, in one implementation, the RF physical model may beconstructed using an RF prediction model of the coverage area, usingmathematical techniques like ray-tracing, and the like. In oneimplementation, the RF prediction model can be computed for eachcoordinate location in a desired physical space. The estimated signalstrength or attenuation information for each AP can be used to populatethe RF coverage maps discussed above. If symmetry (often called“duality”) is assumed between the propagation of signals betweenwireless nodes and the APs, the RF coverage maps for each AP can be usedto estimate the location of wireless nodes by subtracting the estimatedattenuation at each coordinate location from an assumed uniform transmitpower for a mobile station or rogue AP. However, if the transmit powerof the wireless node is assumed to be equal to the APs, then the RFcoverage maps can be used without modification.

In addition, the RF coverage map database can be populated inalternative manners. The RF coverage maps can be populated with theresults of a site survey, according to which a wireless transceiver ismanually placed at different locations in the physical space. During thesite survey, the APs operate in a transmitting mode that cycles betweentheir respective antennas, and include an antenna identifier intransmitted frames. In one implementation, the wireless transceiver,which may be a laptop computer or other wireless device, can beconfigured to transmit the signal strength/antenna data back to an APfor collection by the WLAN management module 10. The RF coverage mapsare initially constructed by associating the signal strength andlocation data in the RF coverage maps corresponding to each AP antenna.Mechanisms that allow the RF coverage maps to be updated are desirable,since the RF environment may change. As described further below, theWLAN management module 10 uses wireless clients to subsequently act assite survey tools and update the RF coverage map.

D.2. Location of a Wireless Client

FIG. 7 is a flowchart illustrating a method for locating a client, inaccordance with one implementation of the present invention. As FIG. 7illustrates, the WLAN management module 10 first receives a selection ofa wireless client, and then selects the access points that will be usedto collect data used to locate that client (702). In one implementation,the WLAN management module 10 may allow a user to select an “all users”command that repeats the foregoing process for all wireless clientsassociated with the system at the point in time that the command wasexecuted. To select a wireless client, WLAN management module 10 mayscan the association tables of one or more access points 50.Furthermore, WLAN management module 10 may select a wireless client thatis associated with an AP, but also has been idle for a threshold periodof time. The selection of APs can be based on the APs that neighbor theAP to which the client is currently associated. The WLAN managementmodule 10 then transmits a location command to the selected APs thatidentify the wireless client and the channel on which to operate (704).In one implementation, the AP to which the wireless client is currentlyassociated transmits one or more test packets to the selected wirelessclient (e.g. 60 a). A test packet causes the wireless client to transmitat least one responsive packet. All selected APs switch to the channelidentified in the location command, monitor for the responsive packet(s)transmitted by the selected wireless client, and record the receivesignal strength and arrival times of the responsive packets.

In one implementation, the present invention can take advantage of acommonly available software utility whereby the wireless clientautomatically responds to the one or more test packets transmitted bythe access point. For example, a Packet Internet Groper (PING) is asmall utility that sends an Internet control message protocol (ICMP)echo request to a selected host and waits for a response (ICMP ECHO).The network protocol stack implemented on the large majority of wirelessclients automatically respond to the ICMP echo request with an ICMP ECHOresponse. As discussed above, the selected access points monitor forthese responses, recording the times of arrival and the receive signalstrength. As one skilled in the art will recognize, the number of testpackets and their spacing is a matter of engineering or design choice.

After the WLAN management module 10 receives the signal data from theselected APs (706), it computes the location of the selected wirelessclient based, in one implementation, on the recorded arrival times ofthe responsive ICMP ECHO packets (708). In another implementation,selected local clients may be enabled with a proprietary locationtechnology—Q-track, infra-red, laser, etc.—to provide a very reliable,accurate location estimate. In one implementation, the WLAN managementmodule 10 may average or otherwise filter the data that results from themultiple test packets. The WLAN management module 10 may then comparethe received signal strength indicators reported by the selected accesspoints to the values stored in the corresponding RF coverage maps at thecomputed location (710) and update one or more of the RF coverage mapsas required. That is, these RSSI values can be used to update the signalstrength values stored in corresponding location bins of the coveragemaps as described below.

In one implementation, the WLAN management module 10 attempts toindependently locate wireless clients. In another implementation, a“dynamic model,” the WLAN management module 10 assumes that the wirelessclient is traveling in a direction with a velocity (e.g., stopped ormoving) that can change. The WLAN management module 10 may constrain theallowed wireless client locations from moment to moment and hence canfilter out implausible estimates of wireless client locations.

D.3. RF Coverage Map Update

The WLAN management module 10 may use the resulting data to refine oneor more RF coverage maps. FIG. 8 is a flowchart illustrating a methodfor updating an existing RF coverage map, in accordance with oneimplementation of the present invention. As FIG. 8 illustrates, afterthe WLAN management module 10 computes an estimated location of thewireless client, the WLAN management module 10 retrieves the existing RFcoverage maps for the selected APs (or the APs that detected wirelessframes transmitted by the wireless client) and the detected receivesignal strength values (802). For a given AP/coverage map pair (803),the WLAN management module 10 compares the coverage map value at theestimated location to the detected receive signal strength values (804).If the detected intensity value differs from the intensity value in thecoverage map, the WLAN management module 10 adjusts the correspondingcoverage map at the wireless client location (806). As discussed in moredetail below, the detected value can also be used to adjust the coveragemap at locations that neighbor the estimated client location. If theintensity values do not differ, the predicted intensity value is notchanged. In one implementation, the coverage map and detected valuesmust differ by a threshold margin for WLAN management module 10 toadjust the RF coverage map. Smoothing algorithms can also be used toadjust the RF coverage map. For example, the signal strength values inthe coverage maps may be adjusted based on the new receive signalstrength using vector algorithms, such as exponential weighted movingaverages, weighted moving averages, and the like. As FIG. 8 illustrates,WLAN management module 10 can repeat this process as desired for allcoverage maps corresponding to the selected APs 50 (803).

In one implementation, any adjustments in signal strength or attenuationvalues in a given location bin in a coverage map may be used to biasadjustments to the values in neighboring location bins, using knowninterpolation or smoothing in space algorithms. Whether neighboringlocation bins are updated based in interpolation may depend on apredetermined threshold difference in computed values or may depend onthe distances between particular location bins. Propagation data storedwith an RSSI-independent coordinate system (e.g., the XYZ coordinatesystem) can be readily updated as new RSSI data becomes available. Inone embodiment of the present invention, where there is no existing RFcoverage map (e.g., after an initial deployment), implementations asdescribed above may be used to generate an initial RF coverage map,which can be updated dynamically as changes to the RF environment occur.WLAN management module 10 may then use the updated RF coverage maps tocompute revised configuration parameters for one or more access pointsof the wireless network system. In addition, graphical representationsof the updated RF coverage maps may be displayed to a networkadministrator to allow for a visual assessment of the RF coverage in adesired region.

The invention has been explained with reference to specific embodiments.For example, while embodiments of the present invention have beendescribed as operating in connection with IEEE 802.11 networks, thepresent invention can be used in connection with any WLAN environment.In addition, while in the embodiments described above, the access pointsare operative to provide signal strength information for wireless nodelocation and to provide wireless service to mobile stations, one or moreof the access points can be configured to operate in a listen-only modeand used solely for location tracking. In addition, while theembodiments described above use SNMP to exchange data, other protocolscan be used, such as XML, SOAP, HTTP, and the like. Other embodimentswill be evident to those of ordinary skill in the art. It is thereforenot intended that the invention be limited except as indicated by theappended claims.

1. A method comprising: receiving first absolute geographic locationdata from each of two or more first wireless access points in a wirelessnetwork, the first absolute geographic location data from each firstwireless access point indicating an absolute geographic location of thefirst wireless access point; receiving relative geographic location datafrom each of one or more of the first wireless access points or one ormore second wireless access points in the wireless network, the relativegeographic location data indicating a relative location of each of oneor more of the first wireless access points and the second wirelessaccess points with respect to each other; determining second absolutegeographic location data indicating an absolute geographic location ofeach of one or more of the second wireless access points based on thefirst absolute geographic location data and the relative geographiclocation data; receiving antenna orientation data from each of one ormore of the first wireless access points or the second wireless accesspoints, the antenna orientation data indicating orientation of one ormore antennae of the first or second wireless access point; andgenerating a radio frequency (RF) model representing RF coverage of oneor more of the first or second wireless access points based at least inpart on the first absolute geographic location data, the second absolutegeographic location data, and the antenna orientation data.
 2. Themethod of claim 1, wherein the relative geographic location datacomprises signal data that indicates received signal strength of signalstransmitted by one or more of the first or second wireless accesspoints.
 3. The method of claim 1, wherein the relative geographiclocation data comprises signal data that indicates times of arrival ofwireless frames carried in signals transmitted by one or more of thefirst or second wireless access points.
 4. The method of claim 1,wherein the first absolute geographic location data is determined usingglobal positioning system (GPS) technology.
 5. The method of claim 1,wherein the relative geographic location data is generated by causing adesired set of the wireless access points in the plurality of wirelessaccess points to switch to a first operating channel, to transmit atleast one wireless frame, and to detect an attribute of the signalstransmitted by other wireless access points in the desired set.
 6. Themethod of claim 1, further comprising communicating the RF model to amodule that automatically determines at least one configurationparameter for the wireless network based at least in part on the RFmodel.
 7. The method of claim 1, wherein the RF coverage of one or moreof the first or second wireless access points is a collective RFcoverage of one or more of the first or second wireless access points.8. The method of claim 1, further comprising updating the first absolutegeographic location data based on the relative geographic location data.9. The method of claim 1, further comprising generating a visualizationof the RF coverage based on the RF model for presentation to a user, thevisualization indicating at least the absolute geographic location ofeach of one or more of the first or second wireless access points. 10.The method of claim 1, wherein the antenna orientation data specifiesone or more of an elevation pattern, an azimuth pattern, or a magneticdeclination.
 11. The method of claim 1: further comprising receivingantenna attribute data from each of one or more of the first wirelessaccess points or the second wireless access points, the antennaattribute data indicating one or more attributes of an antenna of theassociated wireless access point; wherein generation of the RF model isfurther based on the antenna attribute data.
 12. The method of claim 11,wherein the antenna attribute data specifies one or more of antennagain, antenna type, antenna make, antenna model number, or antenna partnumber.
 13. An apparatus comprising: a network interface; at least oneprocessor; a memory; and a configuration application, physically storedin the memory, comprising instructions operable to cause the processorand the network interface to receive first absolute geographic locationdata from each of two or more first wireless access points in a wirelessnetwork, the first absolute geographic location data from each firstwireless access point indicating an absolute geographic location of thefirst wireless access point; receive relative geographic location datafrom each of one or more of the first wireless access points or one ormore second wireless access points in the wireless network, the relativegeographic location data indicating a relative location of each of oneor more of the first wireless access points and the second wirelessaccess points with respect to each other; determine second absolutegeographic location data indicating an absolute geographic location ofeach of one or more of the second wireless access points based on thefirst absolute geographic location data and the relative geographiclocation data; receive antenna orientation data from each of one or moreof the first wireless access points or the second wireless accesspoints, the antenna orientation data indicating orientation of one ormore antennae of the first or second wireless access point; and generatea radio frequency (RF) model representing RF coverage of one or more ofthe first or second wireless access points based at least in part on thefirst absolute geographic location data, the second absolute geographiclocation data, and the antenna orientation data.
 14. The apparatus ofclaim 13, wherein the relative geographic location data comprises signaldata that indicates received signal strength of signals transmitted byone or more of the first or second wireless access points.
 15. Theapparatus of claim 13, wherein the relative geographic location datacomprises signal data that indicates times of arrival of wireless framescarried in signals transmitted by one or more of the first or secondwireless access points.
 16. The apparatus of claim 13, wherein the firstabsolute geographic location data is determined using global positioningsystem (GPS) technology.
 17. The apparatus of claim 13, wherein therelative geographic location data is generated by causing a desired setof the wireless access points in the plurality of wireless access pointsto switch to a first operating channel, to transmit at least onewireless frame, and to detect an attribute of the signals transmitted byother wireless access points in the desired set.
 18. The apparatus ofclaim 13, wherein the configuration application further comprisesinstructions operable to cause the processor and the network interfaceto communicate the RF model to a module that automatically determines atleast one configuration parameter for the wireless network based atleast in part on the absolute geographic locations of the wirelessaccess points.
 19. The apparatus of claim 13, wherein the RF coverage ofone or more of the first or second wireless access points is acollective RF coverage of one or more of the first or second wirelessaccess points.
 20. The apparatus of claim 13, wherein the configurationapplication further comprises instructions operable to cause theprocessor and the network interface to update the first absolutegeographic location data based on the relative geographic location data.21. The apparatus of claim 13, wherein the configuration applicationfurther comprises instructions operable to cause the processor and thenetwork interface to generate a visualization of the RF coverage basedon the RF model for presentation to a user, the visualization indicatingat least the absolute geographic location of each of one or more of thefirst or second wireless access points.
 22. The apparatus of claim 13,wherein the antenna orientation data specifies one or more of anelevation pattern, an azimuth pattern, or a magnetic declination. 23.The apparatus of claim 13, wherein: the configuration applicationfurther comprises instructions operable to cause the processor and thenetwork interface to receive antenna attribute data from each of one ormore of the first wireless access points or the second wireless accesspoints, the antenna attribute data indicating one or more attributes ofan antenna of the associated wireless access point; and generation ofthe RF model is further based on the antenna attribute data.
 24. Theapparatus of claim 23, wherein the antenna attribute data specifies oneor more of antenna gain, antenna type, antenna make, antenna modelnumber, or antenna part number.
 25. An apparatus comprising: means forreceiving first absolute geographic location data from each of two ormore first wireless access points in a wireless network, the firstabsolute geographic location data from each first wireless access pointindicating an absolute geographic location of the first wireless accesspoint; means for receiving relative geographic location data from eachof one or more of the first wireless access points or one or more secondwireless access points in the wireless network, the relative geographiclocation data indicating a relative location of each of one or more ofthe first wireless access points and the second wireless access pointswith respect to each other; means for determining second absolutegeographic location data indicating an absolute geographic location ofeach of one or more of the second wireless access points based on thefirst absolute geographic location data and the relative geographiclocation data; means for receiving antenna orientation data from each ofone or more of the first wireless access points or the second wirelessaccess points, the antenna orientation data indicating orientation ofone or more antennae of the first or second wireless access point; andmeans for generating a radio frequency (RF) model representing RFcoverage of one or more of the first or second wireless access pointsbased at least in part on the first absolute geographic location data,the second absolute geographic location data, and the antennaorientation data.